The present invention relates in general to a dialysis system and method therefor, and more particularly, to such a system and method which compares the value of a measured parameter of the dialysis liquid, e.g., conductivity, blood gases, temperature, pH, and the like, at a location after the dialyzer with a non-measured predetermined set value of the parameter before the dialyzer, whereby the corresponding parameter of the blood of a patient can be theoretically determined and thereby controlled.
In known dialysis systems and treatments, there is generally no feedback of the patient's blood parameters, e.g., temperature, blood gases, electrolyte content, etc., to the dialysis machine. Thus, the value of these patient parameters may become abnormal during the dialysis process without any corrective interaction by the dialysis machine, as long as the dialysis machine is being maintained at the correct parameter set value. Examples of dialysis systems which control the composition of the dialysis liquid irrespective of these blood parameters of the individual patient are known from U.S. Pat. Nos. 4,158,034, 4,293,409 and 4,508,622. Other known dialysis systems are disclosed in U.S. Pat. Nos. 4,194,974, 4,191,359, 4,585,552, 4,536,201, 4,762,618, 4,728,496, and 4,797,655, and European Patent Publications Nos. EP B 22 922 and EP A 204 260.
In U.S. Pat. No. 4,508,622, a dialysis system is disclosed which includes a first detector mounted upstream of the dialyzer and a second detector mounted downstream of the dialyzer by means of which the composition of the dialysis solution can be regulated. The actual measured data of the dialysis liquid from these two detectors are compared and eventually used to control the composition of the dialysis solution. This dialysis system is difficult to control due to the necessity of having to compare two continuously varying measured parameter values before and after the dialyzer.